Two armed robbers who targeted a Sydney bar that was hosting a bikers' meeting must have "failed robber school", said the club's chairman.

The men stormed the bar brandishing machetes and wearing balaclavas - unaware that 50 bikers were holding a meeting in an adjoining room.

Alerted to the robbery, some of the bikers chased the men as they fled.

One was caught after trying to escape through a back door. He was later treated in hospital for minor injuries.

The other man ran off but was arrested by police in a street nearby.

Southern Cross Cruiser Club chairman "Jester" told local media that the robbers had "picked the wrong night".

The would-be bandits had entered the bar and ordered patrons to lie on the floor while they emptied the till.

I can't believe these guys were stupid enough to come into a club with 50 bikers having a bike meeting

Jester

But someone managed to run into an adjoining room where the bikers were holding their monthly meeting.

"We were out there minding our own business and then these guys came to the bar here in the pokey (slot machine) area," Jester told the Sydney Morning Herald.

"One of the guys took off... straight through a glass window, he didn't even bother pushing the button, he just ran straight through it."

Jester said the police were delighted when they arrived on the scene.

"They were really impressed that we caught these guys, because normally they get here and it's all over and done. But we caught the guys, still with their weapons, still in his balaclava and everything else.

"It's a comedy of errors, I can't believe these guys were stupid enough to come into a club with 50 bikers having a bike meeting - just crazy."